Potential immunological approaches to interfere with immune cell-mediated, RANKL-dependent periodontal bone resorption. The central target of these approaches is the inhibition of RANKL expression, secretion and interaction with RANK on osteoclast precursor cells. APC, antigen-presenting cell; CD40 L, CD40 ligand; CRAC, Ca2+ release-activated Ca2+ channels; IL-10, interleukin-10; mRANKL, membrane-bound RANKL; sRANKL, soluble RANKL; NFAT, nuclear factor of activated T cells; OPG, osteoprotegerin; RANK, receptor activator of nuclear factor κB; RANKL, receptor activator of nuclear factor κB ligand; TRAF6, tumor necrosis factor-receptor associated factor 6.